[lwip-users] Query on simultaneous Client and Server using lwip

[Sanchayan]

Hello everyone,

I am using lwip 1.3.2 on Stellaris LM3S6965 ARM Cortex M3 processor and trying to get both server and client working simultaneously.

1. For my application, i am running a server, by initiating a listening connection on Port 2101. On getting a connection request, i serve data as per request. Below is the initialization part.

    // Create a new TCP Protocol Control Buffer abbreviated as PCB.   
      pcb = tcp_new();

    // Bind the PCB to a Port and any IP address.
      tcp_bind( pcb, IP_ADDR_ANY, 2101 );   
   
    // Put the PCB and TCP connection on Board in listening state       
    pcb = tcp_listen( pcb );

    // This function specifies the callback function that will be called when a client asks for connection with board
    tcp_accept( pcb, connection_accept );

2. Another client is running on Port 2103 trying to connect to a server application running on PC for sending data. If connection is established, it sends the data at 5 seconds interval and keeps retrying every 5 seconds if connection fails or is not established.

     err_t conn_err, bind_err ;     

    struct ip_addr ip_addr_server = { 0x4701110A };   
  
    log_pcb = tcp_new();

    bind_err = tcp_bind( log_pcb, IP_ADDR_ANY, 2103 );   
       
    if( bind_err != ERR_OK )
    {
        return bind_err;   
    }
    else if( bind_err == ERR_OK )
        {
            conn_err = tcp_connect(log_pcb, &ip_addr_server, 2103, callback_connected);       
       
        }
  
    return conn_err;   


For the second point, the above is in a function and gets called in the main(),  while(1)  loop of the program. On calling tcp_connect(), i get a ERR_USE -11 Address in Use error. But, my data does get sent, though the data sending is not reliable. A few blocks of data is send, but, no data is sent after sending the first few blocks. I checked in Wireshark, no RST is send and the connection is not closed. Is what i am doing correct and can be accomplished?

On a different note, i also call tcp_write(), in the main loop of the program outside the interrupt context of lwip, for sending data on both connections.  Is this way of using tcp_write correct?.

Any suggestions or help will be most appreciated. Thanks in advance.

Thanks & Regards,
Sanchayan Maity.
Asst Manager | Godrej & Boyce Mfg. Co. Ltd.
Godrej Security Solutions | PSS Tech Cell
Vikhroli, Mumbai - 400709.
Maharashtra, India.

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